1. Field of the Invention
The present invention relates to a method of transforming pixels of a first digital image into pixels of a second digital image, each pixel having a value that indicates a color of the pixel. The method includes the steps of defining a neighborhood of pixels for a pixel of the first digital image, determining a new value for the pixel based on the values of the pixels in the neighborhood, and placing the new value of the pixel in the second digital image. The present invention further relates to an electronic component, a computer program product embodied on at least one non-transitory computer-readable storage medium, and a printing system.
2. Background of the Invention
Digital images are a well-known representation of images. The image is divided in pixels, each pixel being associated with a position in the image, and each pixel being specified by a value of a finite set of quantized values. The set of quantized values refers to colors in a specific color space, usually having more than one dimension. Examples of color spaces are the RGB- and CMYK-color spaces, but also the XYZ-, Lab-, YCbCr-, and HSL-color spaces. A value of a color is formed by the components of a vector in these spaces. In each of these color spaces, a white color is defined. For printing purposes, this white color is often equivalent to the medium color on which the impression is made and therefore corresponds to the no ink color. This color is characterized by zero coverage for all process inks in the appropriate color space. Each color space has its own way of expressing distances between the various colors, either as a Euclidian distance between the points indicated by the vector components or as a multivariable function of the components of the two colors. The color difference between two neighboring pixels is also referred to as the contrast between two pixels.
Digital images stem from a variety of sources, including computer applications, scanners, digital cameras and other kinds of electronic image generators. In these sources, the number of pixels is sufficiently large to contain fine information, This is provided by pixels with a color that is clearly distinguishable from the colors of the pixels around them, when the pixels are rendered on a display or in a printed form. The information is conveyed by the contrast between a pixel belonging to the fine information and the pixels in its neighborhood, which includes pixels that are not more than a few pixel distances away. However, because of limitations of the physical processes at the time of generating the digital image, such as light scattering, or the limitations of the way the digital image is saved electronically, dependent on, e.g. the compression that is used, the contrast between a pixel and the pixels in the neighborhood may be less than necessary for good conveyance of the intended information. Several methods exist, such as discrete laplacian filtering and unsharp masking, that improve the legibility of fine information. Disadvantages of these methods include the enhancement of noise and the possibility of overshoot artifacts. This is especially inconvenient when the information is surrounded by a colored background.
A problem of the present state of the art is the occurrence of the artifacts around fine information when the legibility of fine information is increased. The goal of the present invention is to increase the legibility of the fine information in a digital image without causing artifacts.